feat: add live terminal demo with animated progress bar

Visual demo showing conversation growing from 0% to 100% of context
window, then auto-compacting back to 10% with a structured summary.
Color-coded progress bar, warning states, and summary preview.

Run: npx tsx examples/demo-live.ts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: andrew-iotx